1. Field of the Invention
The invention is directed to a multiple-disk clutch in a drivetrain of a motor vehicle.
2. Description of the Related Art
Multiple-disk clutches of this kind are known. The multiple-disk clutches usually have an outer disk carrier with a spline profile at which outer disks are arranged so as to be fixed with respect to rotation relative to it and axially displaceable and an inner disk carrier with a spline profile at which inner disks are arranged fixed with respect to rotation relative to it and axially displaceable. The outer disks and inner disks are arranged in an alternating manner to form a disk stack. To transmit torque, the disk stack is pressed together by an actuator so that the disks are brought into frictional engagement. The disks can be constructed as steel plates and as faced disks. When actuated, one side of a disk, which has a facing, is always brought into frictional engagement with an adjacent disk which does not have a facing.
The actuator can be constructed as a hydraulically actuated piston. When a multiple-disk clutch of this kind is used as a starting clutch, the torque transmission behavior of the clutch is especially sensitive to torque fluctuations particularly at the beginning of torque transmission in the low torque range. These torque fluctuations have a disproportionately strong impact when the excitation occurring at the rate of rotation of the slipping clutch meets the resonant frequency of the drivetrain. Accordingly, variations in the thickness of individual disks can cause torque fluctuations in the torque transmitted by the clutch which can be transferred to the entire succeeding drivetrain and can lead to jerking of the vehicle or to shaking during starting.
It is known from DE 102 55 537 to arrange resilient springing washers inside the disk stack. Further, it is known from DE 195 30 443 to arrange a disk spring between the piston and the disk stack. Further, it is known from EP 1 577 575 to construct an end disk of a disk stack in such a way that a pressing distribution which is as uniform as possible is achieved when there are high pressing forces.
Fluctuations of the transmitted torque occur when the two sides of the clutch rotate at different speeds such as when starting, for example and the pressing pressure fluctuates due to variations in the thickness of individual disks. The torque always increases when an elevation in a disk passes an elevation in another disk rotating at a different speed, or when the piston or opposite support of the disk stack is in a skewed position and the elevation in a disk passes the narrow point defined by the piston or opposite support. The known springing elements in the disk stack serve to impart an elasticity to the disk stack that can absorb irregularities in torque due to variations in the thickness of individual disks.
However, the known solutions have the disadvantage that the springing elements only make contact in an edge area of the adjacent disk and, therefore, an uneven pressing distribution is introduced into the disk stack. While this unevenness is still not critical when relatively low torques are transmitted such as when starting to move, it is not negligible. In order to optimize the pressing distribution at higher pressing pressures, the springing elements are lightly designed such that the resilient element is pressed flat against the adjacent disk at higher pressing pressures. When the disk stack is actuated by the actuator, the force application radius acting on the disk adjacent to the resilient element shifts gradually from the edge area toward the radial center of the disk stack.